Users and developers of elastic shoes and shoe soles are confronted with the problem of back injury and releasing the stored energy in the shoe sole in a manner which improves walking and running economy while at the same time achieving adequate bio-mechanical shoe stability and cushioning. Many shoe manufacturers have concentrated their effort on chock absorption by permanently increasing the thickness of the shoe sole. This has resulted in a slight change of the angle between the ankle and the foot that may weaken the tendons of the foot. This change of the angle may also lead to instability and reduced bio-mechanical effect. In addition, the focus on increasing the chock absorption within the shoe industry has led to yet another problem, namely the fact that the more cushioning put into a shoe the more energy is needed to get out of it.
Many efforts have been made to develop an effective spring mechanism for shoes or shoe soles in order to come to terms with these and other problems. However, the earlier proposed spring designs for shoe soles have not been satisfactory. Despite many elaborate shoe sole solutions, back injuries and other injuries are still common due to poorly designed shoes. Injuries due to poor shoe designs are common in sports and a variety of work activities.
The method and shoe system of the present invention provide a solution to the above-mentioned problems. For instance will it not only provide sufficient chock absorption/cushioning in order to protect users from injuries related to the stresses of prolonged standing, walking and running. It will also, by its function of storing up energy, provide sufficient energy to heave up the user out of the cushioning, i.e. it does not only absorb energy, it also gives back energy. Furthermore, it does so without risking almost immediate fatigue failure of the resilient shoe insert which is the case with corresponding non-progressive inventions. More particularly, the method is for using a shoe system having a resilient shoe insert. A shoe has a shoe insert disposed inside the shoe. The insert has an upper leg and a lower leg connected by a front end with a curvature. The upper and lower legs 506 have a concave segments and end points. A load is put on the insert to compress the end points towards one another. This shortens the effective length of the legs because the legs are in contact at a contact segment. This makes the insert stiffer the more it is compressed. The effective length of the legs is shorter at the outside compared to the inside so that the outside is stiffer than the inside.
Last but not least, at first glance the present progressively resilient shoe insert may look similar to previous non-progressive ones, but it is not. The closer one looks the lesser resemblances, especially when it comes to functions and qualities. For the sake of clarity, even if it may be crude, one could compare with early days of aviation. It was the shape that was the secret then. Without the wave-profile of the wings, there was no way of taking-off with the airplane. One could say the same about the present invention, at least in a transferred sense. It is the specific and unique wave-shape of the present invention that makes all the difference.